Ventilating devices of this kind are used in motor vehicles to allow for the exhausting of used air from inside of the motor vehicle. However such a device should not contribute to introduce air or contaminants into the motor vehicle inside.
A housing or frame of the ventilating device may be designed also in several parts and is inserted into a vehicle body aperture. Sealing flaps are mounted either pivotably or in flexing manner on the housing. At rest these flaps seal off the housing aperture, but they will move into an open position if the pressure inside the vehicle exceeds that of the outside ambience.
The German patent document DE 293 16 536 U1 discloses a back-air blocking device where the valve flap is made of a resilient material and mounted in a manner to generate a restoring force biasing said flap against the valve seat.
The European patent document EP 1 026 021 B1 discloses making the contact surface between the housing and the valve flap of different materials and keeping said surface small (linear rest). The purpose is to avoid clatter between the flap and the contact surface. The European patent document EP 0 467 095 B1 also discloses making the housing or frame of one piece with the valve flap and to connect latter by a foil hinge to the housing. The European patent document 1 584 508 A1 discloses using different plastics for the housing and the flap when flap and housing are integral. Illustratively such a valve flap is made of a comparatively flexible material whereas the housing is made of a more rigid material. Manufacture is by multi-component injection molding.
It is known from U.S. Pat. No. 5,823,870 to associate the valve flaps with stops precluding the valve flaps from opening excessively or too violently.
The European patent document EP 0 915 302 A2 discloses making valve flaps integrally with, but separate from a housing, knob-like housing protrusions entering apertures in the valve flaps. It is known from the European patent document EP 1 491 373 A1 to make cross-sectionally T-shaped protrusions at the frame which enter slots of resilient valve flaps.
Basically there is a need for the valve flap being easily and reliably displaceable, to be resting as tightly as possible in its closed state against the housing and to generate little or no noise.
Accordingly it is the objective of the present invention to create a back-air blocking device for the inside of a motor vehicle, meeting the above requirements and at the same time allowing very economical manufacture.